Di(2-phenoxyethyl) peroxydicarbonate

ABSTRACT

Di-(2-phenoxyethyl) peroxydicarbonate and improved processes employing same as initiators for the polymerization of ethylenically unsaturated monomers (such as vinyl chloride) and as curing catalysts for curing unsaturated polyester resin compositions.

United States Patent [1 1 Sanchez 1 DIlZ-PHENOXYETHYL) PEROXYDICARBONATE [75] Inventor: Jose Sanchez, Grand Island. NY.

[73] Assignee: Pennwalt Corporation, Philadelphia,

[22] Filed: Oct. 24, I973 [2]] Appl. No.: 409,129

Related U.S. Application Data [62] Division of Ser. No. 209,435, Dec. 17, 1971, Pat. No.

[ Dec. 31, 1974 [56] References Cited UNITED STATES PATENTS 3.657.3ll -l/l972 D'Angelo 260/463 3,720,700 3/l973 Norhack 260/463 3,775,34l Il/l973 Barter 152/426 FOREIGN PATENTS OR APPLICATIONS 1,957,386 7/l970 Germany 260/463 OTHER PUBLICATIONS Chem. Abstracts, Vol. 64, p. 5271b, 1966.

Primary ExaminerI-Iarry Wong, Jr. Assistant Examiner-John Kight Attorney, Agent, or Firm-Plumley & Tyner 5 7 ABSTRACT Di-(Z-phenoxyethyl) peroxydicarbonate and improved processes employing same as initiators for the polymerization of ethylenically unsaturated monomers (such as vinyl chloride) and as curing catalystsfor curing unsaturated polyester resin compositions.

3 Claims, N0 Drawings BACKGROUND OF THE INVENTION a. Field of Invention This invention relates to novel di-(2-phenoxyethyl) peroxydicarbonate (1),

a peroxydicarbonate of unusually high thermal stability which can be transported and stored non-refrigerated, and to its use as a free-radical initiator in polymerizations of ethylenically unsaturated monomers and as a curing catalyst for unsaturated polyester resins.

Dialkyl peroxydicarbonates are low temperature free-radical polymerization initiators (and curing agents) which are displacing the well-known dilauroyl in vinyl chloride polymerizations owing to the superior efficienciesof these initiators. The switch to the lower temperature dialkyl peroxydicarbonates from dilauroyl peroxide was not made without problems, however. Dialkyl peroxydicarbonates such as the commercially available IPP (diisopropyl peroxydicarbonate) have stringent refrigerated storage and shipping requirements which are designed to maintain assay and prevent explosive decompositions upon inadvertent warming. On the other hand, dilauroyl peroxide does not require refrigeration during storage and shipping. Numerous domestic as well-as foreign PVC [poly(vinylchloride)] manufacturers would like to switch from dilauroyl peroxide to the more efficient dialkyl peroxydicarbonates; however, a number of reasons prevent them from doing so. Some domestic PVC producers are not along the routes used by peroxide producers to supply their customers via refrigerated trucks; hence, refrigerated shipments of dialkyl peroxydicarbonates are not frequent. This means th at these producers have to keep large amounts of dialkyl peroxydicarbonates on hand and must receive large shipments of these peroxydicarbonates in order to make it worthwhile (economically) for the peroxide producer to ship to them. Hence, the PVC producers who are not on the refrigerated truck routes must either maintain large and costly refrigerated storage facilities for peroxydicarbonates or they have to use less efficient but more stable dilauroyl peroxide. Another reason that some domestic PVC producers give for not using peroxydicarbonates is the hazard that results from accidental warming to ambient temperatures. IPP will detonate after warming to room temperature. Many foreign PVC producers or potential PVC producers would like to use the more efficient dialkyl peroxydicarbonates for commerical vinyl chloride polymerizations; however, many of these PVC producers are located in countries which do not have manufacturers of dialkyl peroxydicarbonates or of alkyl chloroformates (precursors to peroxydicarbonates) or of phosgene (used to make alkyl chloroformates). This is especially true of PVC producers or potential PVC producers who are located in some of the developing countries of the world such as India, the countries of Southeast Asia, Africa, and Central and South Americas and the Arab nations. Almost all of the developing countries are in the subtropical to tropical areas of the world; hence, ambient temperatures over I00F would not be uncommon. Refrigerated shipment of peroxydicarbonates from producers in the United States or Europe to PVC producers in these developing nations by sea or other carrier would be out of the question owing to thecost of the refrigerated shipmnet and the cost of refrigerated storage to the PVC producer. Hence, there is a need for a dialkyl peroxydicarbonate which can be shipped and stored without refrigeration and one which would survive the highest ambient temperatures which would be encountered without decomposing violently and without losing assay during non-refrigerated transport and storage. Dialkyl peroxydicarbonates which could be useful would, at times, be subjected to temperatures of 50C (122F) and possibly even 60C (F) for short periods of time. Hence, the desired dialkyl peroxydicarbonate would have to survive under these conditions. One peroxide producer determines whether or not a peroxide can be shipped and stored non-refrigerated by testing its thermal stability at 50C for oneweek. If it does not decompose violently during this test, it can be shipped and stored without need of refrigeration. The peroxide producers prefer that the peroxide tested would survive for at least 24 hours at a higher temperature and/or for a longer period of time at 50C since this would result in a greater margin of safety. One thermal stability test which could be run on prospective stable peroxydicarbonates would be a 60C/l day thermal stability test. Since dialkyl peroxydicarbonates usually have 10 hour half-lives (in a solvent) at about 40 to 50C, one would not expect them to survive long at 50C and certainly not long at 60C. In the art, there are many dialkyl peroxydicarbonates which are stable at room temperature (20C to 30C). However, all of these must be shipped and stored refrigerated owing to the high temperature encountered during shipping and storage.

b. Related Art Strain [U.S. Pat. No. 2,370,588 and J.Am. Chem. Soc., 72, 1254 (1950)] discloses the preparations of various dialkyl peroxydicarbonates, including commercially available and hazardous peroxydicarbonates such as IPP. Among those listed is dibenzyl peroxydicarbonate (2) such as di-(4-t-butylcyclohexyl) peroxydicarbonate; Netherlands Application No. 6,917,105 discloses di(- hexadecyl) peroxydicarbonate; German OLS 2,034,922 discloses di-(cis-3, 3, S-trimethylcyclohexyl) peroxydicarbonate; and German OLS 2,034,964 discloses various solid di(bicycloalkyl) peroxydicarbonates such as diisobornyl peroxydicarbonate. As shown below, these compounds are also unstable at temperatures of 3550C.

German OLS 1,957,386 claims room temperature stable peroxydicarbonates of general structure (4):

where R is alkyl or halogen, X is oxygen, and R and R are alkyl groups which can be interrupted with oxygen atoms, and dicloses di-(3-phenoxypropyl) peroxydicarbonate (5):

which is shown below to decompose violently after 8 hours at 50C.

BRIEF SUMMARY OF THE INVENTION This invention concerns: A. Novel di-(Z-phenoxyethyl) peroxydicarbonate, an usually safe and stable peroxydicarbonate; and

B. Improved proces for 1. polymerizing ethylenically unsaturated unsaturated monomers which are responsive at suitable temperatures to initiating amounts of free radical polymerization initiators, and

2. curing unsaturated polyester resin compositions by heating in the presence ofinitiating amounts of free radical curing catalysts,

the improvement residing in the use of di-(2- phenoxyethyl) peroxydicarbonates as said initiator or curing catalyst.

DETAILED DESCRIPTION OF THE INVENTION Dialkyl peroxydicarbonates normally have 10-hour half-lives (in a solvent) at about 4050C. and accordingly are not expected to survive long at 50C. or higher. This is borne out by the fact that dialkyl peroxydicarbonates heretofore disclosed are stable at room temperature but unstable at 50-60C.

Nevertheless, it has now been discovered that di(2- phenoxyethyl) peroxydicarbonate not only passes the 50C test with little or no loss of assay, but also only loses 3 percent ofits assay after 24 hours at 60C. Thus a peroxydicarbonate has now been found which can be transported and stored under almost any temperature condition without need of refrigeration. Polymerization In the free radical initiated polymerization of ethylenically unsaturated monomers at suitable temperatures, the subject peroxydicarbonate is also found to be highly efficient. In fact, it is found to be more than seven times as efficient as lauroyl peroxide (and industry standard) on a molar basis in the polymerization of vinyl chloride, and more efficient on both molar and weight bases than dibenzyl peroxydicarbonate (currently being promoted as a replacement for lauroyl peroxide), even though di-(Z-phenoxyethyl) peroxydicarbonate has a higher molecular weight than dibenzyl peroxydicarbonate.

Suitable monomers include olefins such as ethylene, propylene, styrene, chlorostyrene, vinyltoluene, vinylpyridine, divinyl-benzene and alphamethylstyrene; conjugated olefins such as l, 3-butadiene, isoprene and chloroprene; vinyl esters such as vinyl acetate, vinyl propionate, vinyl laurate, vinyl benzoate and divinyl carbonate; allyl esters such as allyl acetate, diallyl carbonate and diallyl phthalate; unsaturated conjugated nitriles such as acrylonitrile and methacrylonitrile; acrylic acid and methacrylic acid and their esters and amides such as methyl, n-butyl and 2-ethylhexyl acrylates and methacrylates and acrylamide and methacrylamide; maleic anhydride; maleic acid and fumaric acid and their esters; vinyl halo and vinylidene halo compounds such as vinyl chloride, vinyl bromide, vinyl fluoride, vinylidene chloride and vinylidene fluoride; perhalo olefins such as tetrafluoroethylene, hexafluoropropylene and chlorotrifluoroethylene; vinyl ethers such as methyl vinyl ether and n-butyl vinyl ether; acrolein; and mixtures thereof. A preferred monomer is vinyl chloride.

Temperatures of about 0-l50C. (preferably 3575C) and peroxide levels of about 0.003-0.300 percent (preferably 0.0l0.20 percent) by weight, based on the polymerizable monomer, as normally employed in these processes. Conventional solvents can optionally be added to the reaction system.

Curing of Polyester Resins In curing unsaturated polyester resin compositions by heating at suitable curing temperatures in the presence of free radical curing catalysts, the use of di-(2- phenoxyethyl) peroxydicarbonate is found to have greater activity (result in faster cures) than dibenzoyl peroxide (a commercially available low temperature curing catalyst).

Unsaturated polyester resins curable by the invention peroxide normally consist of an unsaturated polyester and a polymerizable monomer.

The unsaturated polyester component is normally obtained by the esterification of one or more ethylenically unsaturated dior polycarboxylic acids or their anhydrides, such as maleic acid, fumaric acid, gultaconic acid, itaconic acid, mesaconic acid, citraconic acid, allylmalonic acid, allysuccinic acid, and others, with saturated or unsaturated polyalcohols such as ethylene glycol, diethylene glycol, triethylene glycol, 1,2- propanediol, l,3-propanediol, .l,2-butanediol, 1,4- butanediol, 2,2-dimethyl -1,3-propanediol, 2-buten- 1,4-diol, 2-butyn-l,4-diol, glycerol, 2,2,4-trimethyl- 1,3-pentanediol, 2,2,4,4-tetramethyl-l ,3- cyclobutanediol, l,4-di(hydroxymethyl)cyclohexane, 1,2,5-hexanetriol, pentaerythritol, mannitol and others. Mixtures of such acids and/or alcohols may also be used. The unsaturated dior polycarboxylic acids may be replaced, at least partly, by saturated, carboxylic acids such as adipic acid, succinic acid, sebacic acid and others, or by aromatic dicarboxylic acids, such as phthalic acid,,tetrahydrophthalic acid, and others and their anhydrides such as phthalic anhydride. The acids used as well as the alcohols employed may be substituted by halogen or other substituents, preferaby by halogen. Examples of such suitable halogenated acids are, for instance, tetrachlorophthalic acid, 1,4,5,6,7,7,-

hexachloro-2,3-dicarboxybicyclo and others, or their anhydrides.

The other component of the unsaturated polyester resin compositions is an ethylenically unsaturated monomer, preferably ethylenically unsaturated monomers such as styrene, chlorostyrene, vinyltoluene, methyl methacrylate, diallyl phthalate, dibutyl fumarate, acrylonitrile, triallyl cyanurate, a-methylstyrene, divinylbenzene,-methyl acrylate, diallyl maleate, ethyl methacrylate, ethyl acrylate and others, which are copolymerizable with said unsaturated polyesters.

A preferred resin composition contains as the polyester component the esterification product of propylene glycol (a polyalcohol), maleic anhydride (an anhydride of an unsaturated dicarboxylic acid) and phthalic anyhydride (an anhydride of an aromatic dicarboxylic acid) and as the monomer component styrene.

Temperatures of from about 20C to about 170C (preferably 50C to 150C) and peroxide levels of from about 0.05 percent to about 5.0 percent or more (preferably 0.2 percent to 2.5 percent by weight of curable unsaturated polyester resin are normally employed.

EXAMPLES The following examples illustrate the subject invention, but are not in limitation thereof.

(2.2.1 )-5-heptene,

Example 1 Preparation of Di-(2-Phenoxyethyl) Peroxydicarbonate (1) 2-Phenoxyethyl chloroformate was prepared in 98.2 percent assay and 92.8 percent corrected yield by reacting 0.35 mole of 2-phenoxyethanol with 0.65 mole of phosgene followed by removal of excess phosgene.

A jacketed reactor equipped with a mechanical stirrer, a thermometer and an addition funnel was charged with 60g. of water and two drops of polyethoxylated nonylphenol (surfactant) and the resulting solution was cooled to C. To it was added 52.0g. (0.26 mole) of 20 percent aqueous sodium hydroxide solution followed by dropwise addition of 885g. (0.13 mole) of H 0 (50 percent). To this vigorously stirred solution at 5C to C was slowly added a solution of 49.0g. (0.245 mole) of Z-phenoxyethyl ehloroformate (98.2 percent) in 75 ml. ofmethylene chloride over a 40 minute period. The reaction mixture was then stirred for 3 hours at 10C to C. To the mixture was added 150 ml. of methylene chloride in order to completely dissolve the product. After separation of the aqueous layer the methylene chloride solution was washed with 40 ml. of 10 percent aqueous sodium hydroxide solution and then with water to neutral. The resulting solution was dried over anhydrous M SQ and, after separation of the used desiccant, the methyTe n e chlo ride was removed in vacuo. The solid product which remained was stirred with cold diethyl ether and after filtration 37.2g. of white solid, mp. 97-100C, was obtained. The assay of the product according to active oxygen content was 99.5 percent, hence the corrected yield was 85.2 percent Example llA Thermal Stabilities of Di-(2-phenoxyethyl) Peroxydicarbonate and Di-(3-phenoxypr0pyl) Peroxydicarbonate Using the method employed in Example 1 di-(3- phenoxypropyl) peroxydicarbonate was prepared with an assay of 92.7 percent and in a corrected yield of 92.0 percent. This material was stirred with cold diethyl ether and the solid was separated by filtration. The product had a melting point of 5153C and had an assay of 98.4 percent according to active oxygen" content. Thermal Stability Test at 50C and 60C In one test 15g. samples of di-(Z-phenoxyethyl) peroxydicarbonate (99.5 percent assay) and of di-(3- phenoxypropyl) peroxydicarbonate (98.4 percent assay) were placed in an oven which was maintained at 50C. The test was stopped if the peroxide decomposed vigorously, otherwise, it was continued and the assay loss was determined after various time intervals. The results are summarized in Example llA Table and show that di-(Z-phenoxyethyl) peroxydicarbonate is unexpectedly more Example IlA Table Thermal Stabilities at 50C Vigorous Total Assay Peroxydicarbonate Decomposition Loss after Di-(2-Phenoxyethyl) No 1.07r/l week Di-(2Phenoxyethyl) No 1.07r/2 weeks Di-(Z-Phenoxyethyl) No 1.07r/4 weeks Di-(3-Phenoxypropyl) Yes l007r/8 hours completely after 8 hours at 50C. On the other hand it is unexpected that di-(2-phenoxyethyl) peroxydicarbonate should survive at 50C for 4 weeks without decomposing vigorously and that it should lose only 1.0 percent of its assay after 4 weeks at 50C.

The slight difference in the assays is not responsible for the observed greater stability of di-(2- phenoxyethyl) peroxydicarbonate over di-(3- phenoxypropyl) peroxydicarbonate since the assay of di-(Z-phenoxyethyl) peroxydicarbonate, after one week at 50C, was about the same as that of di-(3- phenoxypropyl) peroxydicarbonate and it did not decompose or lose any further assay during the next three weeks.

In the other test 15g. of di-(Z-phenoxyethyl) peroxydicarbonate (99 percent assay) was placed in an oven at 60C for 24 hours and the assay was determined. It lost only 3 percent of its assay. Di-(3-phenoxypropyl) peroxydicarbonate was not tested in this way since its behavior at 50C/8 hours would suggest that it would decompose violently after a short period of time at 60C.

Hence, these results show that di-(Z-phenoxyethyl) peroxydicarbonate, the peroxide of this invention, has thermal stability of about 15C higher than that of di-(3-phenoxypropyl) peroxydicarbonate.

EXAMPLE llB Thermal Stabilities of Di-(2-phenoxyethyl) peroxydicarbonate (1) and Di-( l-phenoxy-2-propyl) Peroxydicarbonate (6):

Using the process employed in Example 1 di-(lphenoxy-2-propyl) peroxydicarbonate was prepared. After one recrystallization of the crude product from diethyl ether the product, a solid, mp. 7175C, was obtained in 51.0 percent corrected yield. The assay was 98.0 percent.

ln the thermal stability tests at 50C. g. samples of di-(Z-phenoxyethyl) peroxydicarbonate (99.5 percent assay) and di-( l-phenoxy-2-propy1) peroxydicarbonate (98.0 percent assay) were placed in an oven which was held at 50C. Individual tests were stopped if the peroxide decomposed vigorously, hence the assay loss was considered to be 100 percent. When the peroxide did not decompose vigorously the assay loss was determined after various time intervals. The results are summarized in Example 113 Table and show that di-(2- phenoxyethyl) peroxydicarbonate, the invention peroxide, is unexpectedly more stable than is di-( 1- phenoxy-2-propyl) peroxydicarbonate, a peroxydicarbonate which is structurally similar to di-(Z-phenoxyethyl) peroxydicarbonate.

Example 118 Table Thermal Stabilities at 50C.

EXAMPLE .111

The Thermal Stabilities of Known Solid Peroxydicarbonates Compared to that of Di-(Z-Phenoxyethyl) Peroxydicarbonate Samples of solid peroxydicarbonates such as dibenzyl peroxydicarbonate (US. Pat. No. 2,370,588), di-(4-tbutylcyclohexyl) peroxydicarbonate (US. Pat No. 3,499,919), di(hexadecyl) peroxydicarbonate (Dutch Application No. 6,917,105), di-(cis-3,3,5-trimethylcyclohexyl) peroxydicarbonate (German OLS 2,034,922), diisobornyl peroxydicarbonate (German OLS 2,034,964) and di-(Z-phenoxyethyl) peroxydicarbonate were thermal stability tested at various temperatures. Samples of each were placed in ovens held at the desired temperatures and the assay losses after various intervals of time were determined. These along with the results from Example 11A are summarized in Example 111 Table. These results show that di-(2- phenoxyethyl) peroxydicarbonate, the peroxide of this invention, has much greater thermal stability than any of the known solid peroxydicarbonates. The high thermal stability of di-(2-phenoxyethyl) peroxydicarbonate means that the pure peroxide can be shipped and stored non-refrigerated and will survive without decomposing or losing significant assay for long periods of time at 50C (122F) and will survive without decomposing violently for short periods of time at 60C (140F). No known peroxydicarbonate has thermal stability as great as di-(2-phenoxyethyl) peroxydicarbonate. Its high thermal stability puts it in a class by itself since it can be stored and transported without need of refrigeration, whereas, the others as pure peroxydicarbonates must be refrigerated. While the other so-called stable peroxydicarbonates are stable at room temperature, (1) is room temperature stable as well as stable at the highest ambient temperatures which may occur during transport and storage (50C to 60C).

Example 111 Table Thermal Stability Tests on Solid Peroxydicarhonates Safety Tests on dibenzyl Peroxydicarbonate and Di-(2- phenoxyethyl) Peroxydicarbonate Owing to the fact that dibenzyl peroxydicarbonate is being commercialized as the most thermally stable peroxydicarbonate up to this time, it and di-(2- phenoxyethyl) peroxydicarbonate, the peroxide of this invention, were subjected to various safety tests which are well known (see J. Varjavandi and O.L. Mageliz, Safe Handling of Organic Peroxides, J. Chem. Ed., 48, A451 (1971 which is incorporated herein by reference). The result of these tests are summarized in Example IV Table Example IV Table Safety Tests Peroxydicarbonate Test DMZ-Phenoxyethyl) Dibenzyl Shock sen- Negative at 15 in. Positive at 7 in. sitivity' Rapid Heat Mild explosive at Mild explosion at 94C C Pressure Ves- 1.5 mm. 7.8 mm. sel Test Trauzl 15.5 ml. 18.5 ml.

tests sensitivity of peroxide to iniiiation by shock or impact.

tests sensitivity to decomposition under rapid heating.

compares rate and energy of thermal decomposition under rapid heat and partial confinement.

measures total decomposition force by expansion of a cavity in a lead hloek. and show that di(2-phenoxyethyl) peroxydicarbonate. in every case. is a safer peroxydicarbonate than is dibenzyl peroxydicarbonate.

Example V Vinyl Chloride Polymerization Efficiencies of Dibenzyl Peroxydicarbonate. Dilauroyl Peroxide and Di-(2- phenoxyethyl) peroxydicarbonate at 50C/8 Hrs.

Dibenzyl peroxydicarbonate is being promoted as a thermally stable peroxydicarbonate for dilauroyl perperoxide and di-(2-phenoxyethyl) peroxydicarbonate,

the invention peroxide, required at 90 percent conversion of vinyl chloride. The following recipe was employed in these polymerizations:

Ingredient Parts by Wt.

Vinyl chloride monomer 100 Water (triple distilled) 130 Methocel* (65 HG, 50 cps) (1% aqueous soln.) 60 Aerosol MA** (1% aqueous soln.) 60 Free-radical initiator variable *Methylcellulose (Dow Chemical Co.) "Sodium salt of dihexyl sulfosuccinate (American Cyanamid Co.)

PROCEDURE Pop bottles were employed. Water, aqueous Methocel and aqueous Aerosol MA were added to each bottle and the contents were frozen at -20C. To the bottles were then added varying amounts of free-radical initiators (several bottles for each initiator) and the required amount of liquid vinyl chloride monomer (at -14C). The bottles were crown-capped, enclosed in safety cages and placed in a constant temperature bottle polymerizer maintained at 50C. End-over-end tumbling at a rate of 25 revolutions per minute was employed for agitation and the polymerizations were allowed to proceed for 8 hours. At the end of that time the bottles were removed from the bottle polymerizer, cooled to C and vented of vinyl chloride monomer. Venting of unreacted vinyl chloride monomer seldom took more than 15 to 30 minutes; hence, post-polymerization was insignificant. The amount of polymer produced was determined gravimetrically (by difference in weight) and plots of initiator required versus percent conversion were constructed for each initiator and the amounts of initiators (in grams and in moles) required at 90 percent conversion were determined from the plots. These results are shown in Example V Table and show that Example V Table VCl Susp. Polym. at 50C/8 hours Initiation Reg/100 g.

VCl at 90% Conv. Initiator Grams Mole X 10 DiLauroyl peroxide 0.5500 13.81 Dibenzyl peroxydicarbonate 0.770 2.55 Di-(2-phenoxyethyl) 0.0685 1.89

peroxydicarbonate EXAMPLE VI 100C SPI Exotherms of Di-(Z-Phenoxyethyl) Peroxydicarbonate The unsaturated polyester resin employed in this example was a mixture of an unsaturated polyester and styrene monomer.

The unsaturated polyester was an alkyd resin made by esterifying the following components:

Component Quantity Maleic anhydride l 0 mole Phthalic anhydride I 0 mole Propylene glycol 2.2 moles To the resulting resin was added 0.013 percent by weight of hydroquinone inhibitor. The alkyd resin had an Acid No. of45-50. Seven (7) parts by weight ofthe above polyester (alkyd resin) was diluted with three (3) parts by weight of monomeric styrene. The resulting unsaturated polyester resin had the following properties:

a. Viscosity (Brookfield No.2 at 20 rpm.) b. Specific gravity 13.08 poise Curing Procedure Gelation and cure characteristics di-(2- phenoxyethyl) peroxydicarbonate in the unsaturated polyester resin described above were determined using the Standard SP1 Exotherm procedure for Running Exotherm Curves Polyester Resin, published in the Preprint of the 16th Annual Conference Reinforced Plastics Division, Society of the Plastic Industry, lnc., (February, 1961).

Using this procedure, di-(Z-phenoxyethyl) peroxydicarbonate, the peroxide of this invention, was evaluated as a curing catalyst for the unsaturated polyester resin at C. The level of catalyst employed was that which was equal in active oxygen to 1 percent of dibenzoyl peroxide (a commerically available low temperature curing catalyst). The results are summarized below in Example VI Table.

Example VI Table 100 SPI Exotherms of Di-(Z-Phenoxyethyl) Peroxydicarbonate Gel. Cure Peroxide Min. Min. Peak "F Barcol Di-(Z-phenoxyethyl) Peroxydicarbonate 0.3 1.3 375 25-30 Dibenzoyl Peroxide 1 8 2.7 425 45 of said monomer. 

1. IN A PROCESS FOR THE POLYMERIZATION OF ETHYLENICALLY UNSATURATED MONOMERS, WHICH MONOMERS ARE RESPONSIVE AT SUITABLE TEMPERATURES TO INITIATING AMOUNTS OF FREE RADICAL POLYMERIZA TION INITIATORS, THE IMPROVEMENT WHICH COMPRISES EMPLOYING AS THE INITIATOR AN INITIATING AMOUNT OF D-(2-PHENOXYETHYL) PEROXYDICARBONATE.
 2. Claim 1 wherein the monomer is vinyl chloride.
 3. Claim 2 wherein about 0.01 to 0.20 percent by weight of said initiator is employed based on the weight of said monomer. 